Catalytic hydrocarbon reactions



u y 16,1946; w. P. HAWTHORNE 2,403,922

I CATALYTIC HYDROCARBON REACTIONS Filed Nov. 22, 1944 z sheets sheet 1 L/QU/D FEED hum Elma/mm July 16, 1946. gA T' b E- 2,403,922

CATALYTIC HYDROQ-ARBON REACTIONS Filed Nov. 22, ,1944 2 Sheets-Sheet 2 awe/whom Patented July 16, 1946 UNITED STATES PATENT OFFICE ..2,403,922 CATALYTIC HYDROCARBON REACTIONS Wendell P. Hawthorne, Wenonah, N. J., assignor toSocony-Vacuum Oil Company, Incorporated, a corporation of New York Application November 22, 1944, Serial No. 564,629.

4 Claims. 1

This invention relates to a method for conducting synthetic hydrocarbon reactions in the presence of a liquid acid catalyst, and, is particularly concerned with a preferred embodiment involving alkylation of isoparafiins with olefins in the presence of liquid hydrogen fluoride.

The invention is directed to a method of conducting the processes disclosed and claimed in applications Serial Nos. 481,430 and 490,487, filed April 1, 1943, and June 11, 1943, respectively. According to the earlier of the said applications, reactions such as alkylation and polymerization are conducted in the presence of such liquid acid catalysts as sulfuric acid, hydrogen fluoride and phosphoric acid by injecting the feed hydrocarbons in vapor phase to a liquid phase catalyst. The later of said applications shows advantages obtained by supplying the feed hydrocarbons, in either vapor or liquid phase, at a temperature in excess of that at which the catalyst is maintained. According to either of these processes, a rather heavy heat exchange load is imposed on the system for removal of heat of condensation or sensible heat or both; in addition to the heat of reaction encountered in processes of this type.

It is a primary object of the present invention to provide a method of contacting vapor phase charge hydrocarbons; preferably heated to a temperature above that of the catalyst; to a body of liquid phase catalyst. The method provides for simultaneously abstracting heat from the contacting zone and supplying the desired heat to charge hydrocarbons for vaporization, and heating of vapors if desired, by indirect heat exchange of liquid charge hydrocarbons with liquids in the contacting zone under conditions to induce vaporization of the charge hydrocarbons. This expedient takes advantage of the high latent heat of vaporization to achieve high efiiciency cooling and at the same time achieve the necessary vaporization of the charge.

Further objects and advantages of the invention will be apparent from the discussion below of preferred embodiments of the invention adapted for practice in apparatus shown in the annexed drawings, wherein:

Figure 1 is a diagrammatic view of a reactor for alkylation in the presence of hydrogen fluoride according to the invention; and

Figure 2 is a vertical section of a reactor structure using a double coil heat exchanger.

Referring specifically to Figure 1, a body of liquid hydrogen fluoride occupies the lower portion of an alkylation tower indicated generally at ID. A layer of liquid hydrocarbons overlies the acid; forming an interface therewith at ll. Immersed inv the liquid within tower Ii) are two cooling coils l2 and it; of which coil [2 is adapted to receive liquid phase feed from line H through an expansion valve 15. The feed is expanded to a pressure suitable to induce vaporization in coil i2, thus taking up latent heat of vaporization and cooling the liquids in tower Ill. The coil I3 is connected to a suitable source of cooling medium, such as plant cooling water or a refrigeration system and serves to absorb the heat in excess of that taken up by vaporization of feed in coil l2.

The vapor phase feed is conducted from the outlet of coil, l2 to a, compressor I6, preferably by way of a heat exchanger IT. The heat of compression in compressor I6 serves to supply a considerable portion of the preheat normally desired in operation of the system, but it is usually advisable to adjust the temperature in heat exchanger IT. The preheated compressedfeed from compressor l6 passes by line I8 to an atomizer, such as the atomizing plate IS in the bottomof tower id. The atomized charge rises through the 'liquidhydrogen fluoride, which is of sufiicient depth to provide a residence time suitable for satisfactory alkylation. In general, the system should provide for a residence time of at least about 5 seconds. Although the invention contemplates longer residence times, such periods may vary between about 5 and seconds with good results.

As the hydrocarbons, unreacted feed components, and alkylate reach interface ll, they merge into the layer of hydrocarbons above the interface and further reaction is substantially inhibited. The liquid hydrocarbons are withdrawn by line 20 under the control of liquid level controller 21 and transferred to conventional equipment for recovery of product and separation of unreacted hydrocarbons, acid catalyst and heavy ends in the usual manner.

The tower I0 is preferably operated under a temperature and pressure such that a fairly large proportion of unreacted hydrocarbons (principally isobutane in alkylation of isobutane with butenes) and hydrogen fluoride will pass from the hydrocarbon layer in Vapor phase. Any hydrocarbons that can be removed without condensation materially reduce the heat exchange load and evaporation of hydrogen fluoride aids in heat control by requiring latent heat of vaporization. These vapors, containing a small amount of heavier hydrocarbons, pass from the top of the tower by vapor line 22, through heat exchanger 23 and compressor 24 to the charge feed line 18, from which they are again admitted to the tower [0. The vapors from line 22 may be condensed in whole or part, cooled and supplied by way of feed line H! after separation of liquid hydrogen fluoride for separate return.

The embodiment of Figure 2 employs a double coil heat exchanger in which the reaction mixture in an outer tube is cooled by heat exchange with an inner tube in which the charge is vaporized and with a bath of hydrogen fluorid in which the reaction coil is immersed. The reaction is induced in a dispersion of acid catalyst and reactants formed by injecting vaporous reactants from line through a nozzle 25 in the open end of reaction tube 26. The stream of reactants acts to draw catalyst from the liquid body surrounding tube 26 and efficiently disperse the reactants in the flowing stream so induced. The liquid feed is admitted to inner coil 12 through expansion valve l5 from feed line 14 and is vaporized in coil l2 to cool the reaction mixture. A cooling medium is also circulated in heat exchange relationship with the body of catalyst, as

by jacket 21, thus providing a cooling bath about reaction coil 28. The feed vaporized in coil I2 and vapor recycle from line 22 are handled in much the same manner as in Figure 1.

In a typical run, the alkylation was conducted at about 80 F. and 100 pounds per square inch absolute by maintaining tower in at about those conditions. The vaporous charge was admitted to contact with the catalyst at 200 F. and 150 pounds per square inch absolute and comprised 90 weight per cent of isobutane and weight per cent of butene. The advantages of the invention are strikingly illustrated by these typical conditions. Even if the system is operated to remove all hydrocarbons, including unreacted excess isobutane, in liquid phase; about half of the cooling required for cooling the reaction zone is supplied by vaporization of charge. About 75% of the heat required for vaporization and pre heating of charge is derived from heat exchange with the reaction mass. Where a large proportion of unreacted isobutane is withdrawn from the reaction zone in vapor phase, in accordance with preferred practice, the cooling load is greatly reduced, since condensation of vapors is the greatest factor. Under these conditions, a correspondingly larger share of the cooling efiect is obtained from vaporizing of the charge in heat exchange relationship with the reaction mass.

I claim:

1. In a process for synthesizing valuable hydrocarbon products by exothermic reaction of an isoparaflin and an olefin in the presence of liquid hydrogen fluoride, the steps which comprise maintaining a reaction zone containing said liquid hydrogen fluoride under conditions favorable to said reaction such that the products of said reaction will be predominantly liquid and the reactants will be predominantly vaporous, introducing to said liquid hydrogen fluoride a vapor phase feed containing isoparaflin and olefin prepared as hereinafter described to thereby induce said reaction with formation of a liquid product while permitting unreacted material to remain predominantly in the vapor phase, removing liquid hydrocarbons from said reaction zone and recovering the product therefrom, preparing a liquid phase fresh charge mixture containing isoparafifin and olefin, vaporizing and expanding said charge mixture in indirect heat exchange relationship with said liquid hydrogen fluoride to thereby cool said reaction zone, withdrawing vaporous unreacted hydrocarbons from said reaction zone and mixing them with said vaporized charg mixture to form said vapor phase feed and introducing said vaporized feed to said liquid hydrogen fluoride as aforesaid.

2. The process of claim 1 wherein said isopararnn is isobutane and said olefin is butene.

3. In a process for synthesizing valuable hydrocarbon products by exothermic reaction of an isoparafin and an olefin in the presence of liquid hydrogen fluoride, the steps which comprise maintainin a reaction zone containing said liquid hydrogen fluoride under conditions favorable to said reaction such that the products of said reaction will be predominantly liquid and the reactants will be predominantly vaporous, introducing to said liquid hydrogen fluoride a vapor phase feed containing isoparaifin and olefin prepared as hereinafter described to thereby induce said reaction with formation of a liquid product while Permitting unreacted material to remain predominantly in the vapor phase, removing liquid hydrocarbons from said reaction zone and recovering the product therefrom, preparing a liquid phase fresh charge mixture containing isoparaffin and olefin, vaporizing and expanding said charge mixture in indirect heat exchange relationship with said liquid hydrogen fluoride to thereby cool said reaction zone, withdrawin vaporous unreacted hydrocarbons from said reaction zone and mixing them with said vaporized charge mixture to form said vapor phase feed and introducing said vaporized feed to said liquid hydrogen fluoride as aforesaid; said vapor phase feed being adjusted to a temperature in excess of the temperature of said liquid hydrogen fluoride before introduction thereto.

4. The process of claim 3 wherein said isoparaflin is isobutane and said olefin is butene.

WENDELL P. HAWTHORNE. 

